1. Field of the Invention
The present invention relates to an ingot cutting method, especially to an ingot cutting method capable of reducing damage rate.
2. Description of the Related Art
An ingot dicing process generally requires the steps of: (a) attaching a glass plate onto a steel holder by applying a layer of epoxy between a back surface of the glass plate and a front surface of the steel holder; (b) attaching an ingot onto the glass plate by applying a layer of epoxy between a back surface of the ingot and a front surface of the glass plate; (c) wire sawing the ingot to get a plurality of wafers (d); and removing epoxy remnants from the plurality of wafers (e).
In the process mentioned above, the glass plate is used to provide an indication of complete cutting of the ingot when part of it is sawn; and the epoxy remnants are generally removed by placing the glass plate and the wafers in hot water for a period of time.
However, as the ingot, which can have a round cross sectional shape or a rectangular cross sectional shape for manufacturing semiconductor products or photovoltaic products, is generally made from brittle materials, part of the wafers can be damaged during the dicing process.
In a typical manufacturing facility, losses of wafers resulting from the dicing process are around 2%, and this problem can get worse when the thickness of wafers is expected to be as thin as possible to reduce material cost.
To avoid the damage of wafers, one solution is to provide a more sophisticated wire sawing apparatus as that disclosed in U.S. Pat. No. 8,256,407. U.S. Pat. No. 8,256,407 provides a multi-wire saw which, at the start of cutting of an ingot, is capable of preventing a wire from being displaced from grooves of guide rollers by utilizing a wire-lifting restraining member, and this can improve the cutting quality.
Although this approach can improve the ingot cutting performance, however, the sliced wafers are still easy to fracture due to the brittle characteristic inherited from the ingot.
To solve the foregoing problem, a novel ingot cutting method is needed.